I'm wanting to install a water softener. Can I merge the drain pipe from the softener with the line coming from the relief valve on the top of the water heater? I'm concerned about the elevation of where I would need to merge the pipe, in respect to the exit port on the softener.

  • Are you talking about the exhaust pipe where the "smoke" from the gas flame exits? Or are you talking about the drain line attached to the pressure relief valve?
    – longneck
    Dec 24, 2014 at 18:36
  • @longneck lol no sorry the discharge line coming from the relief valve
    – rhill45
    Dec 24, 2014 at 18:48
  • I have one. And gas heat, and a gas stove until my wife decided she wanted a glass top stone.
    – longneck
    Dec 24, 2014 at 18:51
  • I'm unable to quote any code but it seems to me like this is a bad idea. Hopefully someone else can supply a definitive answer.
    – longneck
    Dec 24, 2014 at 19:04

1 Answer 1


The down pipe from your water heater relief valve should not be plumbed into a drain. the output end may be hovering over a floor drain but not hard plumbed to drain lines. If the relief blows off due to high pressure (possibly steam) it could rupture a hard plumbed drain line.

There are two drain lines from a water softener; one over-flo from the brine tank and one off the control valve. The over-flo line could go to the same place as the heater relief output. The line from the control valve will have a significant pressure while the softener is in recharge or backwash modes and should be hard plumbed through a check valve to your drain piping to sewer or septic.

  • Thanks good info here. It's the high pressure line from the resin tank I was worried about. I'm finding a lot of plumbers who just hover it 6" over a floor drain like the down pipe from my heater is. However the pipe would have to elevate significantly before it meets the with the water heater pipe.
    – rhill45
    Dec 25, 2014 at 4:42

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